Question

A manufacturer of banana chips would like to know whether its bag filling machine works correctly at the 449 gram setting. It is believed that the machine is underfilling the bags. A 23 bag sample had a mean of 448 grams with a standard deviation of 20. A level of significance of 0.05 will be used. Assume the population distribution is approximately normal. Determine the decision rule for rejecting the null hypothesis. Round your answer to three decimal places.

Answer 1

We accetp H₀

Explanation:

Information:

Normal distribution

Population mean = μ₀ = 449

Population standard deviation σ unknown

Sample size n = 23 n < 30 we use t-student test

so n = 23 degree of fredom df = n - 1 df = 23- 1 df = 22

Sample mean μ = 448

Sample standard deviation s = 20

Significance level α = 0,05

1.-Hypothesis Test

Null hypothesis H₀ μ₀ = 449

Alternative hypothesis Hₐ μ₀ ≠ 449

Problem statement ask for determine decision rule for rejecting the null hypothesis. For rejecting the null hypothesis we have to get an statistic parameter wich implies that μ is bigger or smaller than μ₀

2.-Significance level α = 0,05 ; as we have a two tail test

α/2 = 0,025

Then from t - student table for df = 22 and 0,025 (two tail-test)

t(c) = ± 2.074

3.- Compute t(s)

t(s) = ( μ - μ₀ ) / s /√n

plugging in values

t(s) = (448 - 449) / 20 /√23 ⇒ t(s) = - 1*√23 /20

t(s) = - 0.2398

4.-Compare t(c) and t(s)

t(s) < t(c) - 0.2398 < - 2.074

Therefore t(s) in inside acceptance region. We accept H₀